Overhead sectional door assemblies are in common use in both residential and industrial building structures. A typical conventional sectional door assembly (a) is shown in FIG. 1a. 
The sectional door assembly (a) comprises a door (m) having several vertically stacked door panels (b) connected together along their abutting edges by metal hinges (not shown). Each door panel (b) supports a pair of roller hinges (d) at its upper corners. Each roller hinge (d) has a roller (e) which engages and runs along one of a pair of C-shaped tracks (f) secured to the jamb (g) at the sides of the door opening.
Each track (t) has a lowermost, upwardly extending section (i), an uppermost, inwardly extending, generally horizontal section (j) and a curved corner section (k) joining the upwardly extending and horizontal sections (i), (j). The curved corner section (k) usually has a single radius, typically falling in the range 12-15 inches, and bends through about 90°.
A torsion spring lifting assembly (l) is commonly provided to lift the sectional door (m). This lifting assembly (l) usually comprises a horizontal shaft (n) rotatably mounted to the header or jamb (g) above the door opening (h). The shaft (n) carries a cable drum (o) at each of its ends. A torsion spring is connected to and coiled around the central portion of the shaft (n). A lift cable is connected between each drum (o) and the underlying bottom corner of the sectional door (m). If the tensioned torsion spring is released, it rotates the shaft (n) and drums (o) and winds in the cables, thereby lifting the door (m) along the tracks (f).
A door operator (not shown), usually comprising a jack shaft driven by an electric motor, is commonly provided to push the door (m) toward the upright closed position from the horizontal open position.
Together, the door operator and torsion spring lifting assembly require a significant amount of space or “headroom” above the door. Typically, in a residential garage case, about 10-12 inches of headroom is needed. If the headroom is reduced an inch or two, this will bring the cable drums (o) closer to the top of the sectional door (m). There is then a risk that the upper end of the top panel (b) will contact the cable drums (o) as the panel travels through the curved corner track sections (k).
Builders have long pressed manufacturers of sectional door assemblies for reduction in headroom requirements.
It has been conventional to incline the upwardly extending sections of the tracks away from the door jamb, from the bottom to the top. This is done primarily to break the door (m) away from the weather stripping (t) so that the door will not wear the stripping as the door moves up and down. It has also allowed the headroom to be reduced to about 10-12 inches.
The use of inclined tracks, however, carries with it the penalty of having to use “wedge-type hardware”. By this is meant that the track mounting brackets, which connect the tracks (f) to the door jamb (g), and the panel roller hinges (d) necessarily are “stepped” or vary in size. It will be appreciated that, while the sectional door (m) is to roll along inclined tracks, it still needs to be vertical when closed, to press against the weather stripping (t) mounted on the vertically oriented door jamb and thereby provide an effective seal against wind. To accomplish this, wedge-type hardware needs to be used. Wedge-type hardware is expensive.
With this background in mind, it therefore is one object of the present invention to modify a sectional door assembly so that it can work in a reduced headroom, for example in the order of 8 to 10 inches.
It is a preferred object to provide an assembly that does not need inclined tracks and wedge-type hardware.